Lack of emotional support is associated with higher blood pressure (BP) and increased risk of cardiovascular death. Laboratory studies indicate that contact with a supportive spouse or friend acts as a stress buffer, lowering BP and cortisol responses to stressors. Oxytocin is a neuropeptide related to milk ejection in mothers, but also plays an important role in emotional bonding between mother and infant, and between spouses/partners. Study 1 of the proposed project will focus on oxytocin and the bond between spouses/partners by comparing plasma oxytocin, BP, vascular resistance, and other cardiovascular (CV) HPA-axis and catecholamine responses to stress in couples reporting high versus low marital support and satisfaction, and in these groups versus socially isolated age mates (n=180). Study 2 will attempt to replicate the investigators' prior findings regarding mothers of infants who are high versus low oxytocin responders in a larger sample, and will extend this study to include a group with cocaine exposure during pregnancy, and also a group of fathers of infants (n=100). Both studies will examine lab stress responses both after a period of close physical contact with their babies/partners or substitutes and after a control period spent alone. Relationships of oxytocin and emotional support to ambulatory BP, urinary cortisol and catecholamines to real life demands at home will also be examined via ambulatory monitoring. Study 3 will retest 24 high and 24 low oxytocin responders from Studies 1 and 2 after intravenous infusion with exogenous oxytocin versus placebo, in a within subject, counterbalanced treatment order. The association of lack of supportive parents in childhood to current low oxytocin, low perceived support and excessive stress responses will also be examined. The investigators believe that the findings will add to knowledge about the cardiovascular stress buffering benefit of emotional bonds between family members, with particular focus on oxytocin's direct and indirect roles as a modulator of cardiovascular, emotional and behavioral responses.